Synthesis, Characterization, In Vitro Cytological Responses, and In Vivo Bone Regeneration Effects of Low-Crystalline Nanocarbonated Hydroxyapatite

Abstract

Hydroxyapatite (HA) has been commonly used as an alternative bone substitute. But it has drawbacks, such as poor degradation and limited osteogenesis. Low-crystalline carbonated hydroxyapatite (L-CHA), which has greater biodegradability than HA, is suggested as one of the main components of bone minerals, but the exact mechanism behind the roles of carbonate substituted in biological behaviors of low-crystalline HA is still a mystery. In this study, L-CHAs with different carbonate contents were prepared, and the effects of the content on the physicochemical properties, in vitro cytological responses, and in vivo bone defects repair effects of L-CHAs were investigated. The results demonstrated that CO 3 2− had successfully entered the lattice structure of L-CHAs with a maximum content of 9.2 wt %. Both low-crystalline undoped HA (L-HA) and L-CHAs were nanocrystalline (20−30 nm) with significantly higher specific surface areas, protein adsorption capacities, and biodegradability compared to high-crystalline HA (H-HA) with submicron crystalline size (200− 400 nm). Besides, the amounts of the adsorbed protein and released Ca 2+ ions increased in a carbonate-content-dependent manner. Compared to L-HA and H-HA, L-CHAs promoted the adhesion and proliferation of bone marrow mesenchymal stem cells and significantly upregulated the levels of alkaline phosphatase (ALP) activity and the expression of osteogenesis-related genes. In addition, L-CHA-9 not only showed a faster biodegradation rate but also effectively promoted bone regeneration when implanted in the critical-sized bone defects of rabbit femora. This study provided evidence for the development of L-CHA as a promising biodegradable and bioactive material with great osteoconductivity and osteogenic capability with respect to conventional HA.

Scalable Fabrication of Polymeric Composite Microspheres to Inhibit Oral Pathogens and Promote Osteogenic Differentiation of Periodontal Membrane Stem Cells

“…The bioactive agents used in this work were epigallocatechin gallate (EGCG) and nano-hydroxyapatite (nHA). EGCG, a major polyphenolic compound extracted from green tea, is a promising alterative to antibiotics and displays high antibacterial activity against typical Gram-positive and Gram-negative bacteria, i.e., Escherichia coli and Staphylococcus aureus. , nHA is a principal inorganic constituent of human bones and has been widely used for bone repair due to its excellent bioactivity and osteoinductivity. − Morphological and structure observation verified the success in the preparation of composite microspheres, which showed fast and sustained release of EGCG and Ca 2+ ions, respectively. We evaluated the antibacterial capacity of the composite microspheres against two representative oral pathogens, i.e., P.…”